Hypertension affects nearly one in eight adult Americans. In its most common form it appears as the insidious onset of an elevated blood pressure, and is thus often a chronic process when discovered. The anatomic lesion in chronic hypertension is a fixed change in the walls of arterioles resulting in increased peripheral vascular resistance. The morphologic correlate is an increase in the extracellular matrix of the blood vessel wall. In the aorta this matrix contains a diverse group of structural macromolecules and these are increased in amount as a result of chronic hypertension. The composition of the extracellular matrix in normal or hypertensive arterioles is not known. Since changes in this compartment appear fundamental to the development of chronic hypertension, this is an important gap in current knowledge. The proposal is therefore focused on the extracellular matrix in normal and hypertensive renal arterioles. The kidney was chosen because it is prominently affected in hypertension. Since the arterioles cannot be isolated for biochemical studies their composition will be assessed by using affinity-purified antibodies to matrix components. The antibodies will be tagged and applied to kidney sections and the amount and distribution of staining will be determined. Two models of hypertension will be used, one which is genetically determined (the spontaneously hypertensive rat) and one induced surgically (Goldblatt hypertension in the rat). Rats in each group will be treated to determine whether matrix changes are reversible or preventable. Finally, renal biopsies and autopsies from patients with hypertension will be examined.